Developmental Psychology

Chapter 9: Human Development[pic 1]

Module 9.1: Prenatal Development

• Developmental psychology- the branch of psychology that explores physical, emotional, cognitive, and social aspects of development.
• Prenatal development brings into focus the long-debated debate of nature vs. nurture (environment vs. genes)
• Maturation is the biological unfolding of an organism according to the underlying genetic code. It largely determines how organisms grow and develop physically.
• Nature and nurture shape development even in the womb.

Stages of Prenatal Development

• Sexual reproduction began about 240-320 million years ago, according to scientists.
• Males: XY sex chromosomes
• Females: XX sex chromosomes
• Each reproductive cell or germ cell (sperm in males, ovum in females) contains only one copy of the two sex chromosomes.
• During ovulation, an ovum is released and then makes its way through the fallopian tube. If fertilization occurs, the combination of the sex chromosomes determines the baby’s sex.
• The single cell is called a zygote. It undergoes cell division (meiosis).
• A nine-month pregnancy is divided into three trimesters.
• The three major prenatal stages are the germinal stage (roughly the first two weeks after conception), the embryonic stage (two-eight weeks after conception), and the fetal stage (until birth).
• The germinal stage:

• From fertilization to the implantation in the wall of the uterus.

• The embryonic stage:

• From implantation to about the eighth week.
• Major organ systems begin to form in the embryo.
• The neural tube is formed three weeks into the pregnancy; a primitive heart forms and beats by the fourth week
• The embryo is suspended in a protective environment called the amniotic sac surrounded by amniotic fluid (shock absorber).
• Nutrients and waste materials are exchanged through the placenta by the umbilical cord. Their blood streams do not mix

• The fetal stage:

• Begins around the ninth week.
• All of the major organ systems are formed including fingers and toes.
• The fetus increases more than thirty-fold in weight during the second trimester-from one ounce to two pounds; from four to fourteen inches.
• By the end of the second trimester, the fetus approaches the age of viability (capable of sustaining life on its own).

• Full term: 38 weeks.

Threats to Prenatal Development

• Maternal malnutrition is associated with a greater risk of premature birth (birth prior to 37 weeks of gestation) and low birth weight (< 5 lbs).
• The federal government recommends all women of childbearing age to take 400 micrograms of vitamin B (folic acid) and that pregnant women take 800 micrograms.
• Folic acid greatly reduces the risk of neural tube defects such as spina bifida.
• Teratogen: derived from Greek root teras (“monster”).
• Teratogens include harmful drugs, X-rays, environmental contaminants (lead & mercury), and infectious organisms.

Infectious Diseases

• Rubella, also called German measles, is a common childhood disease that can lead to serious birth defects including heart disease, deafness, and mental retardation.
• Women exposed to rubella in childhood acquire immunity. Those who lack immunity may be vaccinated.
• Some STDs such as HIV/AIDS and syphilis may be transmitted from mother to child during pregnancy.
• However, an aggressive treatment of the antiviral drug AZT for HIV-infected mothers reduces the risk of transmission.
• Children with congenital syphilis may suffer liver damage, impaired hearing and vision, and deformities in their teeth and bones.
• The risk of transmission may be reduced if the infected mother is treated with antibiotics prior to the fourth month of pregnancy.

Smoking, Alcohol, and Drugs

• Maternal smoking can lead to miscarriage, premature birth, low birth weight, and increased risk of infant mortality. It is also linked to increased risks of Sudden Infant Death Syndrome (SIDS), lung problems (asthma), and developmental problems such as reduced attention span, learning problems, and behavioral problems.
• Fetal Alcohol Syndrome (FAS) causes mental retardation and facial deformities such as a flattened nose, an underdeveloped upper jaw, and widely spaced eyes.
• FAS may occur in babies whose mothers drink as little as two ounces of alcohol a day during the first trimester. There is no established safe limit for alcohol use.

Module 9.2: Infant Development

Reflexes

• A reflex is an unlearned, automatic response to a particular stimulus.

• Rooting reflex: the reflexive turning of the newborn’s head in the direction of a touch on its cheek.
• Eyeblink reflex: the reflexive blinking of the eyes that protects the newborn from bright light and foreign objects.
• Sucking reflex: rhythmic sucking in response to stimulation of the tongue or mouth.
• Moro reflex: when the infant extends its arms, arches its back, and brings its arms toward each other in response to a sudden noise or loss of support.
• Palmar grasp reflex: the reflexive curling of the infant’s fingers around an object that touches its palm
• Babinski reflex: the reflexive fanning out and curling of the infant’s toes and inward twisting of its foot when the sole of the foot is stroked.

Sensory and Perceptual Ability

• Vision is the slowest of the senses to develop.
• Infants have about 20/400 vision at birth which corrects to 20/20 by age 5.
• Newborns show preferences for looking at facelike patterns over nonfacelike patterns. They can recognize their own mother’s face and show its preference.
• By 1 month of age, an infant can follow a moving object.
• By 2 months, the infant has developed basic color vision.
• Depth perception develops by around 6 months.
• By using a visual cliff apparatus, Eleanor Gibson and Richard Walk showed that most infants 6 months and older have developed depth perception.
• Newborns are particularly sensitive to sounds falling within the frequency of the human voice. They can discern their mother’s voice from others.
• By several months of age, infants can differentiate among various speech sounds.
• At 5 to 6 days of age, infants can detect their mother’s odor. They can also discriminate among different taste and show preferences for sweetness.
• Newborns are sensitive to a soothing voice, the way in which they are held, and can recognize a scrambled picture of their mother’s face.
• By age 4 to 6 months, babies can discriminate among happy, angry, and neutral facial expressions and show a preference for faces reflecting their own racial characteristics.

Learning Ability

• Infants can learn simple responses and retain memories of learned behaviors for days or weeks.
• 2 to 6 month-year-olds can learn and remember a kicking response that activates a crib mobile.
• 6 to 7 month-year-olds can retain memories for faces and for sounds of particular words.
• Newborns prefer their mother’s voice and for sounds reflecting their native language.

Motor Development

• Newborns’ motor skills are not limited to simple reflexes.
• Minutes after birth, newborns can imitate their parents’ facial expressions.
• During the first three months, infants slowly replace reflexive movements with voluntary, purposive movements.
• By the second or third month, they begin bringing objects to their mouths.
• By about six months, they can reliably grasp stationary objects and begin catching moving objects.
• By two months, infants can lift their chins; by five months, they can roll over; by nine months, they can sit without support.
• By the end of the first year, infants will stand up without support.
• Because of their smaller size, infants will sway about 40% more while standing than adults. They also have less time to respond to balance disturbances.

Module 9.3: Years of Discovery-Emotional, Social, and Cognitive Development in Childhood

• Childhood is a period of wonderment, discovery and change.
• Stage theorists such as Erikson (psychosocial development) and Piaget (cognitive development) believe that development remains relatively stable within each stage but then abruptly jumps to the next stage.

Temperament: The “How” of Behavior

• Temperament- a characteristic style of behavior or disposition; the “how” of behavior.
• The New York Longitudinal Study (NYLS)